How get the called function to loggin with decorators?

Question

I want to write to a log file some events. In order to do this I've used functions decorators to add the loggin code, and report the function called. But, the output is always the same function, the decorator function _decorador.

I'm using the %(funcName)s parameter in format logging.basicConfig

Output in example.log:

04/21/2014 09:32:41 AM DEBUG This message should go to the log file _decorador
04/21/2014 09:32:41 AM INFO So should this _decorador
04/21/2014 09:32:41 AM WARNING And this, too _decorador
04/21/2014 10:46:23 AM DEBUG This message should go to the log file (debug) _decorador
04/21/2014 10:46:23 AM INFO So should this (info) _decorador
04/21/2014 10:46:23 AM WARNING And this, too (warning) _decorador

Desired output in example.log:

04/21/2014 09:32:41 AM DEBUG This message should go to the log file mi_funcion
04/21/2014 09:32:41 AM INFO So should this mi_funcion
04/21/2014 09:32:41 AM WARNING And this, too mi_funcion
04/21/2014 10:46:23 AM DEBUG This message should go to the log file (debug) mi_funcion
04/21/2014 10:46:23 AM INFO So should this (info) mi_funcion
04/21/2014 10:46:23 AM WARNING And this, too (warning) mi_funcion

My code:

#!usr/bin/python3
# -*- coding: UTF-8 -*-

import logging

FORMAT = '%(asctime)s %(levelname)s %(message)s %(funcName)s'
logging.basicConfig(filename='example.log', level=logging.DEBUG, format=FORMAT, datefmt='%m/%d/%Y %I:%M:%S %p')

# Decorator function, writes in the log file.
def decorador(funcion):
    def _decorador(*args, **kwargs):
        funcion(*args, **kwargs)
        logging.debug('This message should go to the log file (debug)')
        logging.info('So should this (info)')
        logging.warning('And this, too (warning)')
    return _decorador

    @decorador
def mi_funcion(arg1, arg2):
    print("Code asset: %s; Registry number: s%" % (arg1, arg2))

mi_funcion("18560K", 12405)

Answer 1

You cannot easily change this. The goal of the logging module funcName is to report exact locations of the source code line, not the function it represents. The idea is that you use it in combination with the lineno and filename entries to pinpoint the source code, not what function was called.

In order to achieve this, the log module uses code object introspection to determine the real function name:

def findCaller(self):
    """
    Find the stack frame of the caller so that we can note the source
    file name, line number and function name.
    """
    f = currentframe()
    #On some versions of IronPython, currentframe() returns None if
    #IronPython isn't run with -X:Frames.
    if f is not None:
        f = f.f_back
    rv = "(unknown file)", 0, "(unknown function)"
    while hasattr(f, "f_code"):
        co = f.f_code
        filename = os.path.normcase(co.co_filename)
        if filename == _srcfile:
            f = f.f_back
            continue
        rv = (co.co_filename, f.f_lineno, co.co_name)
        break
    return rv

Short of reconstructing the _decorador code object you cannot alter what is reported here. Reconstructing the code object can be done; you could build a facade function with exec that calls the decorator, for example. But for this to work with a closure is more work than you should worry about, really.

I'd instead include the function name of the wrapped function:

logging.debug('This message should go to the log file (debug) (function %r)', 
              funcion)